#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>

int main() {
    char n;
    scanf("%c", &n);
    if (n >= 'a' && n <= 'z' || n >= 'A' && n <= 'Z')
    {
        printf("YES");
    }
    else
    {
        printf("NO");
    }
    return 0;
}